Eusociality is the social structure in which one individual reproduces, and the others rear her offspring. Queen honeybees produce QMP, which represses reproduction in their workers. This repression is through the highly conserved Notch cell signalling pathway. Interestingly, the non-social, 350 million year diverged Drosophila melanogaster also has their reproduction impaired by exposure to honeybee QMP, similar to the repression observed in worker bees.
We aim to understand how eusociality has evolved in honeybees, in particular how queen mandibular pheromone (QMP) induces reproductive constraint in the worker caste. We are using the easily manipulable and genetically tractable Drosophila melanogaster to investigate this process.
Confirming previously published results; we show that QMP exposure causes a significant reduction in the number of mature oocytes in Drosophila ovaries. We have demonstrated that this response is plastic and reversible by removing Drosophila from the QMP source and allowing ovarian development to proceed, leading to a significant recovery of phenotype. RNA-seq is currently being carried out on ovaries from QMP exposed Drosophila across various time points, as well as those with recovered phenotypes. This allows us to identify genes that alter their expression during this removal of QMP.
That Drosophila responds to QMP despite being so diverged, implies that there may be ancestrally conserved mechanisms by which insects respond reproductively to their environment that have been co-opted into this role in honeybees.